In this proposal, we wish to examine the structure-function relationships of the clot-dissolving enzyme, plasmin, and its precursor molecule, plasminogen. Toward this end, we intend to selectively degrade the plasminogen molecule, sequentially removing regions which bind to fibrinogen and fibrin and epsilon-amino caproic acid. With these modified proteins in hand, we can assess the importance of these regions of the molecule toward several different physical and chemical characteristics (e.g., activation rate, plasmin kinetics, etc.).